Tension leg connection system and method of installing

Abstract

A floating construction having a base, a tensioning member extending from the sea bed in the direction of the base, a connector at an upper end of the tensioning member and attachment elements on the base for attaching to the connector, characterized in that, the attachment elements include a guide member for lowering a tensioning member section by a predetermined distance, which tensioning member section at a free end is provided with a complementary connector for attaching to the connector on the upper end of the tensioning member, the tensioning member section including at an upper end a stopper for engaging with the base and for fixing and/or adjusting the upper end in a vertical direction, the floating construction including a pulling device attached to the tensioning member section, for lowering the tensioning member section along the guide member towards the tensioning member.

The invention claimed is: 
     
       1. A method of installing a floating structure comprising a hull having a base ( 2 ), comprising:
 providing pre-installed vertically oriented tendons ( 17 , 18 ) having upper ends ( 16 , 19 ) submerged below sea level at an installation site; 
 floating the structure to the installation site; 
 ballasting the structure to an installation draft level; 
 lowering a tendon section ( 12 , 13 ) from the base by a distance below a bottom of the base ( 2 ), substantially in line with a respective pre-installed tendon ( 17 , 18 ), towards an upper end of the respective pre-installed tendon which at its upper end is provided with a connector ( 27 , 28 ), via a pulling device ( 36 , 37 , 38 , 39 ) on the floating structure that is attached to the tendon section ( 12 , 13 ); 
 connecting the connector at an upper end of the pre-installed tendon with a complementary connector ( 25 , 26 ) at a lower end of the tendon section; 
 fixing the tendon section on the base; and 
 exerting a tensioning force on the interconnected tendon and tendon section by deballasting the base and placing the base in a moored state wherein a lower end of the tendon section is placed at a distance (D 2 ) below the bottom of the base of between 1 m and 200 m. 
 
     
     
       2. The method according to  claim 1 , wherein the complementary connector is lowered along a guide wire towards the connector on the pre-installed tendon. 
     
     
       3. The method according to  claim 1 , wherein the complementary connector is lowered towards the connector on the tendon via a remote operating vehicle. 
     
     
       4. The method according to  claim 1 , wherein the lower end of the tendon section is placed at the distance (D 2 ) below the bottom of the base of between 5 m and 50 m. 
     
     
       5. A floating structure ( 1 ), comprising:
 a hull having a base ( 2 ); 
 a tendon ( 17 ,  18 ) extending from a sea bed in a direction of the base; a connector ( 27 ,  28 ) at an upper end ( 16 ,  19 ) of the tendon ( 17 , 18 ); and 
 a tendon section ( 12 ,  13 ) connected at an upper end thereof to the base and having at a lower end a complementary connector ( 25 ,  26 ) attached to the connector ( 27 ,  28 ), the connectors being situated at a distance (D 2 ) below the base bottom wherein the distance (D 2 ) in a moored state of the floating structure construction is between 1 m and 200 m; and 
 wherein the attachment is accomplished by lowering the tendon section ( 12 ,  13 ) from the floating structure. 
 
     
     
       6. The floating structure according to  claim 5 , wherein the base comprises for each tendon section a respective relatively light-weight pulling device ( 36 , 37 , 38 , 39 ) that is adapted for lowering of a respective tendon section, the pulling device having a raising power that is lower than the power required for pulling down the floating structure to a deeper draft level. 
     
     
       7. The floating structure according to  claim 5 , wherein the tendon ( 17 , 18 ) is provided with a buoyancy member ( 29 , 30 ) at or near the connector ( 27 ,  28 ). 
     
     
       8. The floating structure according to  claim 5 , wherein in the moored state the distance (D 2 ) of the floating construction is between 5 m and 50 m. 
     
     
       9. A floating construction ( 1 ), comprising:
 a hull having a base ( 2 ); 
 a tendon ( 17 ,  18 ) extending from the sea bed in the direction of the base; 
 a connector ( 27 ,  28 ) at an upper end ( 16 ,  19 ) of the tendon; and 
 attachment means ( 12 ,  13 ,  14 ,  15 ,  25 ,  26 ,  33 ,  34 ) on the base for attaching to the connector ( 27 ,  28 ), the attachment means comprising a guide member ( 14 ,  15 ) for lowering a tendon section ( 12 ,  13 ) by a predetermined distance (D 2 ) below a bottom of the base ( 2 ), the tendon section ( 12 , 13 ) at a free end ( 23 ,  24 ) being provided with a complementary connector ( 25 ,  26 ) for attaching to the connector ( 27 ,  28 ) on the upper end ( 16 ,  19 ) of the tendon ( 17 ,  18 ), the tendon section comprising at an upper end ( 31 ,  32 ) a stopper ( 33 ,  34 ) for engaging with the guide member ( 14 , 15 ) and for tensioning the tendons ( 17 , 18 ) upon deballasting of the base ( 2 ), the floating construction comprising a pulling device ( 36 ,  37 ,  38 ,  39 ) attached to the tendon section ( 12 ,  13 ), for lowering the tendon section ( 12 ,  13 ) along the guide member ( 14 ,  15 ) towards the tendon ( 17 ,  18 ), until the upper end ( 31 ,  32 ) is fixed in a vertical direction and the lower end of the freely depending tensioning member section ( 12 , 13 ) extends substantially in line with the tensioning member ( 17 , 18 ) while the complementary connector ( 25 , 26 ) is situated at the predetermined distance (D 2 ) below the bottom wherein the predetermined distance (D 2 ) in the moored state of the floating construction is between 1 m and 200 m. 
 
     
     
       10. The floating structure according to  claim 9 , wherein in the moored state the distance (D 2 ) of the floating construction is between 5 m and 50 m.